This invention relates generally to optical communication systems and components. More particularly, the invention relates to optical systems comprising microelectromechanical (MEMS) components.
In the field of telecommunication, it is recognized that optical communication components and systems that use light waves to carry information, employing such components as infrared solid state lasers and the like, and fiber optic cables and similar communication media, offer many considerable advantages over conventional copper wire-based communication systems that communicate using electrical signals to carry information. One advantage has to do with the greater amount of information that can be carried by a single physical connection using a single fiber optic strand as compared to a copper wire circuit.
At present, however, there exists no simple, convenient and cost effect technology for directing, switching, adding, removing, and otherwise manipulating information carried by optical signals that flow through fiber optic strands, or cables comprising a plurality of such strands, in the form of light. A very much simplified description of the present situation in the field of optical communication illustrates the need for appreciable improvements in optical communication components.
If a simple two station direct voice telecommunication link using optical technology existed, it would operate by converting vocal information input at the first station into electrical signals, converting the electrical signals to optical signals, and transmitting the optical signals via a fiber optic strand from the transmitter station to a receiver station. The receiver station would accept the optical signals, the optical signals would be converted into electrical signals, and the electrical signals would be converted into information in a form, such as sound, that a party holding the handset of the receiving station can sense.
However, in a real telephone network using commercial state of the art optical communication technology, involving a station that can call any of a plurality of other stations, it becomes necessary to switch signals for routing purposes. The electrical signals that are generated at the first receiving station (which is now a central office) are switched in the same manner as are the standard electrical signals carried by copper wire communication circuits, and are then reconverted to optical signals. The optical signal is sent along a fiber optic strand, possibly to one or more intermediate stations, where the conversion and reconversion process occurs again, until the signal finally reaches its destination. It would be advantageous to be able to do all of the signal switching and manipulation without having to repeatedly convert optical to electrical signals and electrical signals to optical signals. In particular, it would be useful if such signal switching and manipulation could be accomplished simply, conveniently and in a cost effect manner.
The optical bench of the present invention provides solutions that eliminate the limitations and deficiencies previously described. The optical bench provides a core component that makes possible the capability of performing all of the necessary switching, adding, dropping, and manipulating of optical signals entirely in the optical domain, without having to convert any signal to an electrical signal from an optical signal, or the reverse. The optical bench can have, among different embodiments, monolithic structures that are fabricated conveniently by the methods of micromachining from single substrates, such as silicon wafers and the like.
Micromachining of silicon, as an example, allows manufacturing with good yield, in a technology that employs well developed fabrication methods on a material that is relatively inexpensive and is readily obtained. Furthermore, the structures so produced are all part of, or are connected to, a single wafer of a solid material, and are therefore likely to maintain alignment under the stresses of thermal changes, mechanical shocks, and the like. To the extent that the optical bench core structure is made of a well understood semiconductor material, it is also possible to build control circuitry directly into the semiconductor wafer, further simplifying the interconnection of the optical bench with external control circuitry such as computers and the like.
In one aspect, the invention features an optical apparatus that includes a wavelength dispersive optical element receiving a substantially collimated input signal having multiple wavelengths and providing a wavelength dispersed output signal, and a spatial modulator element receiving the wavelength dispersed output signal and providing an output signal comprising at least a portion of each dispersed wavelength.
In one embodiment, the optical apparatus further includes a second wavelength dispersive optical element receiving the output signal provided by the spatial modulator and providing a substantially collimated output signal. The substantially collimated output signal can be directed in substantially the same direction as that of the substantially collimated input signal.
The optical apparatus can additionally include an absorbing surface that absorbs selected dispersed wavelengths of the spatial modulator output signal, the spatial modulator controlling selection of the wavelengths. The selection of the dispersed wavelengths to be absorbed can be controlled dynamically by the spatial modulator. In addition, the optical apparatus can include a variable reflection filter. Alternatively, the optical apparatus can include a variable transmission filter.
In another aspect, the invention features an optical apparatus that includes a wavelength dispersive optical element receiving a substantially collimated input signal propagating in a first direction, the input signal having multiple wavelengths, and providing a wavelength dispersed output signal, a spatial modulator element receiving the wavelength dispersed output signal and providing an output signal comprising at least a portion of each dispersed wavelength, and the wavelength dispersive optical element receiving the output signal provided by the spatial modulator and providing a substantially collimated output signal propagating in a second direction. In one embodiment, the second direction of propagation is substantially opposite to the first direction of propagation.
In still another aspect, the invention features an optical apparatus that includes a wavelength dispersive optical element receiving a substantially collimated input signal propagating in a first direction, the input signal having multiple wavelengths, and providing a first wavelength dispersed output signal and a second wavelength dispersed output signal, a spatial modulator element receiving the first wavelength dispersed output signal and the second wavelength dispersed output signal and providing a transmitted output signal and a reflected signal, and a collimating optical element receiving the reflected signal and providing a substantially collimated output signal propagating in a second direction substantially opposite to the first direction.
In one embodiment, the wavelength dispersive optical element and the collimating optical element are the same optical structure viewed from opposite ends thereof. In another embodiment, one of the transmitted output signal and the reflected signal comprises a signal modulated to have substantially zero intensity.
In a further aspect, the invention features a monolithic optical apparatus that includes a wavelength dispersive optical element receiving a substantially collimated input signal having multiple wavelengths and providing a wavelength dispersed output signal, and a spatial modulator element receiving the wavelength dispersed output signal and providing an output signal comprising at least a portion of each dispersed wavelength, wherein the wavelength dispersive optical element and the spatial modulator element are provided on a single substrate.
In yet another aspect, the invention features a microelectromechanical optical apparatus that includes a wavelength dispersive optical element receiving a substantially collimated input signal having multiple wavelengths and providing a wavelength dispersed output signal, and a spatial modulator element receiving the wavelength dispersed output signal and providing an output signal comprising at least a portion of each dispersed wavelength.
The wavelength dispersive optical element and the spatial modulator element can be provided on a single substrate. In one embodiment, the single substrate comprises a single crystal. In another embodiment, the single substrate comprises a semiconductor single crystal. In yet another embodiment, the single substrate comprises polycrystalline material.
The foregoing and other objects, aspects, features, and advantages of the invention will become more apparent from the following description and from the claims.